#1Xiaobo Yu(DST: Defence Science and Technology Organisation)H-Index: 1
Abstract The spliced wing panels on a surveillance aircraft are subject to sequentially applied axial and shear load cycles. This paper aims to propose an approach to address the fatigue crack growth under this scenario. Current understanding on fatigue crack growth behaviours was reviewed, focusing on crack surface interferences and fatigue crack growth mechanisms under non-proportional mixed-mode loads. A generic spliced plate was analysed using non-linear finite element modelling. The analysi...
Abstract Cyclic non-proportional loading is common experimental practise for investigations of large structures like vehicles. Numerical analysis of local non-proportional loading conditions is also a well established field of research and application. However, theoretical and practical support is rare for evaluating the growth of fatigue cracks under non-proportional cyclic loading conditions. At least seven influence factors – most of them not yet thoroughly understood – are listed and discuss...
Abstract A significant portion of the fatigue life is typically spent in growth of small cracks. In addition, the stress state in many structures and components is multiaxial. Therefore, the study of small crack growth behaviour with regards to its growth path as well as growth rate under combined stresses can be of great importance in many applications. This study investigates small crack growth behaviour of several steels under multiaxial states of stress. Experimental observations from solid ...
Fatigue crack growth tests were performed under various mixed-mode loading paths, on maraging steel. The effective loading paths were computed by finite element simulations, in which asperity-induced crack closure and friction were modelled. Application of fatigue criteria for tension or shear-dominated failure after elastic–plastic computations of stresses and strains, ahead of the crack tip, yielded predictions of the crack paths, assuming that the crack would propagate in the direction which ...
#2Sylvie Pommier(École normale supérieure de Cachan)H-Index: 19
Mode II fatigue crack growth tests as well as tests in sequential mode I and then mode II were performed on ferritic-pearlitic steel. For ΔKII ranging from 7 to , bifurcation occurs after 12–450 μm of coplanar growth at a decreasing speed. By contrast, hundreds of micrometres of constant speed coplanar growth were obtained under sequential mode I and then mode II loading, for and ΔKI ranging from 0.25 to 1.0 ΔKII. The crack growth rate is a simple sum of the contributions of each mode for ΔKI= 0...
#2Andras Abel(USYD: University of Sydney)H-Index: 3
Abstract The sliding contact mechanism proposed in Part I of this publication is quantitatively analysed with the assumption of rigid asperity and Coulomb friction. A discrete step-wise iteration program, with a capability to cope with opening, sticking, bottom touching, down and uphill sliding, is developed to solve the crack surface interference under cyclic mode I and steady mode II loads. The effects of plastic/oxidation-induced crack closure combined with sliding contact are considered by i...
#2Andras Abel(USYD: University of Sydney)H-Index: 3
Abstract This paper reports experimental studies related to crack surface interference (CSI) under mixed mode conditions. It focuses on the features other than the well-recognized mode I or shear mode crack closure. Firstly, the near-tip strain gauge method, which was traditionally used for mode I crack closure measurement, was extended to mixed mode conditions. Two approaches were proposed to separate mode I and mode II related strains from raw strain readings. The sensitivity and free surface ...
A previous modelling analysis predicted that crack surface interference under cyclic shear loads is a combination of cyclic shear attenuation and cyclic wedge-opening. In the present study, experimental evidence is provided on notched thin-walled tubular specimens to evaluate the modelling predictions. Tests were carried out with varied static tensions superimposed on fully reversed (R τ = -1) or pulsating (R τ = 0) cyclic shear loads. The crack surface interference was measured by near-tip stra...
Crack surface interference under cyclic shear loads is studied by an analytical method. The proposed model simulates the effects arising from both the residual stresses and the asperity interactions. A closed-form and a discrete approach are presented in obtaining the crack surface interference solutions. Backlashes of shear displacements, peeling or group sliding behaviours and induced cyclic mode I stress intensities are predicted under three configurations of residual stress distributions. Th...
Abstract This work has been an attempt to improve fatigue life estimation of the Epsilon TB-30 fleet of aircraft under Portuguese Air Force operation. To this end, a finite element model of the main frame was created using knowledge from strain gauges and accelerometers data as well as the loads placed on the aircraft. This model allowed the authors to identify critical areas on the structure and granted information about the stress field around these. The first estimate on fatigue life was calc...
#1Amin Saber(FUM: Ferdowsi University of Mashhad)H-Index: 2
#2Mahmoud Shariati(FUM: Ferdowsi University of Mashhad)H-Index: 21
Last. Reza Masoudi Nejad(University of Electronic Science and Technology of China)H-Index: 14
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Abstract The main factor in determining path and rate in fatigue crack growth (FCG) problems is the stress field around the crack tip that is defined as stress intensity factor (SIF). Cutouts cause a stress concentration that depends on their size and geometry. This stress concentration can affect the stress field near the crack tip vicinity and deviates the FCG path. In this paper in order to study the effect of cutout parameters on FCG, first, a taguchi statistical analysis is used. Then, cont...
An increasing number of the offshore structures in the North Sea are being operated in a life extension phase, which means that their original design life has been exceeded. As the structures age, they are deteriorating, mainly due to fatigue and corrosion. In order to ensure that the structural integrity is maintained during the life extension phase, the remaining fatigue life of the structures needs to be assessed. While simple and conservative approximations are used in fatigue design, it wil...
#1R. Baptista(IPN: Instituto Politécnico Nacional)H-Index: 9
Abstract Mixed mode fatigue crack growth (FCG) can occur due to complex loading or specimen geometry. Fatigue crack paths can be determined using propagation criteria like the Maximum Tangential Stress (MTS) criterion, or the Maximum Shear Stress (MSS) criterion, for mode I and II dominated propagation respectively. These criteria only consider mode I and II Stress Intensity Factors (SIF), neglecting the T-Stress effects. In order to develop a new fatigue crack propagation model, that takes this...
Abstract Environmental loads acting on structures usually cause fatigue crack propagation under variable amplitude mixed-mode conditions. In order to better estimate the remaining fatigue life, the fatigue crack growth behaviour under these conditions needs to be studied. In this paper, an experimental study where mixed-mode I and II overloads are applied to a fatigue crack propagating under mixed-mode I and II constant amplitude loading, is presented. The overloads are found to cause fatigue cr...
Last. Eugenio Giner(Polytechnic University of Valencia)H-Index: 22
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Abstract A proper prediction of crack paths is required when assessing accurately the fatigue crack propagation life. Recently, some authors have pointed out that the criterion of minimum shear stress range leads to inconsistent results when predicting fretting crack paths under incomplete contacts. In this paper, different fretting experiments with cylinder-to-flat contact found in the literature are reviewed, and the corresponding crack path prediction using the extended finite element method ...
#1Xingquan Zhang(Anhui University of Technology)H-Index: 8
#1Xingquan Zhang(Anhui University of Technology)H-Index: 1
Last. Guangwu Fang(Anhui University of Technology)H-Index: 3
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In the paper, the propagation processes of two parallel cracks in 2-mm-thick plate pulled by the cyclic loading were investigated by numerical simulation and experiment. The codes Abaqus and Franc3D were implemented jointly to predict the crack growth path, the stress distribution around the cracks tip and the fatigue life. The corresponding fatigue experiment was carried out on a servo-hydraulic fatigue testing machine. The investigation indicates that the predicted crack paths agree well with ...
#1Yajun Chen(CAUC: Civil Aviation University of China)H-Index: 5
#2Chenchen Liu(CAUC: Civil Aviation University of China)H-Index: 3
Last. Fusheng Wang(CAUC: Civil Aviation University of China)H-Index: 3
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Abstract Due to the seawater splash, rain water scouring and prolonged exposure, the aircrafts serviced in sea-coast or marine environment always suffered liquid corrosion effects under certain temperature. 2024-T4 aluminum alloy had been widely used in aircrafts fuselage. During service, the actual process was close to the alternate mode of “Ground Corrosion + Air Fatigue”, in which alternate corrosion factors had greatly effects on multiaxial fatigue life of 2024-T4 aluminum alloy. For the pur...